Agricultural harvesters, or combines, are large machines that harvest, thresh, separate and clean an agricultural crop. The resulting clean grain is stored in a grain tank located on the combine. The clean grain can then be transported from the grain tank to a truck, grain cart or other receiving bin by an unloading auger. There are three basic types of combines: (1) a conventional combine having a transverse threshing cylinder for threshing the harvested crop, and straw walkers for separating the threshed crop; (2) a hybrid combine having a transverse threshing cylinder for threshing the harvested crop, and one or more separator rotors within a housing for separating the threshed crop; and (3) a rotary combine having a rotor within a housing for threshing and separating the harvested crop.
In conventional and hybrid combines, the crop processing unit comprises a transverse threshing cylinder mounted in close proximity to a grate called a concave. The rotating threshing cylinder in conjunction with the fixed concave threshes the crop material. The concave generally comprises a series of transversely extending bars through which are inserted axially running wires. A concave of this type forms a grate through which the majority of the threshed grain and chaff fall onto a collecting assembly where it is directed to the cleaning system of the combine. U.S. Pat. Nos. 4,909,772 and 5,024,631 each disclose a conventional transverse concave for a conventional combine. In hybrid combines with rotary separation, the crop processing unit additionally comprises one or more rotors surrounded by a housing. The bottom of the housing is provided with a series of separating grates through which the grain and chaff fall from the housing.
Rotary combines are provided with an infeed section for pulling crop material into the rotary crop processing unit from the feederhouse, a threshing section for threshing the crop material, and a separating section for separating the grain from the threshed crop material. The rotary crop processing unit comprises a rotor that is surrounded by a housing. The bottom of the housing is provided with a series of grates through which the grain and chaff fall from the housing. The grates located beneath the threshing section of the rotary crop processing unit comprises a concave, such a concave is disclosed in U.S. Pat. No. 4,499,908. In this patent one side of the concave is pivotally mounted to the crop processing unit and the other side is adjustably mounted to the crop processing unit to control the clearance between the concave and rotor. U.S. Pat. Nos. 5,613,907 and 6,193,604 each disclose a concave for a rotary combine.
Crop material, especially green crop material and high volume crop material, tends to plug the concave, not allowing grain to pass through the concave and thus reducing capacity and threshing ability. Often, removal of the concave is required in order to clear the plugged material. Furthermore, in some rotary combines, it is necessary to change between two different concaves, with different sized openings, when changing between harvesting of small and large grain crops. Thus, it is desirable that mounting means for the concave provide for ease of attachment and removal.